Tungsten film forming method, film forming system and film forming apparatus

ABSTRACT

A tungsten film forming method in which a substrate having a TiN film formed thereon is disposed in a processing container and a tungsten film is formed above a surface of the substrate while heating the substrate in a reduced pressure atmosphere, includes forming a first film of an aluminum-containing material on the substrate and forming the tungsten film on the first film.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2018-006529, filed on Jan. 18, 2018, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

Various aspects and embodiments of the present disclosure relate to atungsten film forming method, a film forming system and a film formingapparatus.

BACKGROUND

When manufacturing LSI, tungsten is widely used for a MOSFET gateelectrode, a contact with source/drain, a word line of a memory, and thelike. In a multilayer wiring process, a copper wiring is mainly used.However, copper is poor in heat resistance and is easily diffused. Forthis reason, tungsten is used for parts requiring heat resistance, partsfor which deterioration of electrical characteristics due to copperdiffusion is a concern, and the like.

A physical vapor deposition (PVD) method was previously used fortungsten film formation processing. However, it is difficult for the PVDmethod to cope with a portion requiring high coverage (step coverage).For this reason, a chemical vapor deposition (CVD) method with good stepcoverage is used for tungsten film formation processing.

When forming a tungsten film by the CVD method, from the viewpoint ofadhesion to a silicon layer and suppression of a reaction, there hasbeen used a method in which a TiN film is formed as a barrier layer on asilicon layer and a tungsten film is formed thereon. In this method, anucleation process for facilitating uniform tungsten film formation isperformed prior to main film formation of the tungsten film by the abovereaction.

However, the tungsten film produced by the nucleation process(hereinafter also referred to as “nucleation film”) has a highresistance. Therefore, when thinning the entire tungsten film, thetungsten film has a high resistance due to the influence of thenucleation film portion.

In LSI, a wiring is miniaturized, and reduction in resistance of awiring is required. For example, in a three-dimensional stackedsemiconductor memory such as a 3D NAND flash memory or the like, atungsten film is formed as a word line. For purposes of miniaturization,it is required to further reduce the resistance of the tungsten film.

SUMMARY

Some embodiments of the present disclosure provide a technique capableof reducing the resistance of a tungsten film even when the tungstenfilm is made thin.

According to one embodiment of the present disclosure, there is provideda tungsten film forming method in which a substrate having a TiN filmformed thereon is disposed in a processing container and a tungsten filmis formed above a surface of the substrate while heating the substratein a reduced pressure atmosphere, including: forming a first film of analuminum-containing material on the substrate; and forming the tungstenfilm on the first film.

According to another embodiment of the present disclosure, there isprovided a film forming system, including: a first film formingapparatus including a first processing container, a first exhaust part,a first heating mechanism and a first gas supply mechanism including analuminum-containing gas supply source; a second film forming apparatusincluding a second processing container, a second exhaust part, a secondheating mechanism and a second gas supply mechanism including a tungstengas supply source; and a control part, wherein the control part isconfigured to control the first exhaust part, the first heatingmechanism, the first gas supply mechanism, the second exhaust part, thesecond heating mechanism and the second gas supply mechanism so as toperform: forming a first film of an aluminum-containing material on asurface of a substrate having a TiN film formed thereon in the firstprocessing container while heating the substrate in a reduced pressureatmosphere; and forming a tungsten film on the first film in the secondprocessing container while heating the substrate having the first filmformed thereon in a reduced pressure atmosphere.

According to another embodiment of the present disclosure, there isprovided a film forming apparatus, including: a processing container; anexhaust part; a heating mechanism; a gas supply mechanism including analuminum-containing gas supply source and a tungsten-containing gassupply source; and a control part, wherein the control part isconfigured to control the exhaust part, the heating mechanism and thegas supply mechanism so as to perform: forming a first film of analuminum-containing material on a surface of a substrate having a TiNfilm formed thereon in the processing container while heating thesubstrate in a reduced pressure atmosphere; and forming a tungsten filmon the first film in the processing container while heating thesubstrate having the first film formed thereon in a reduced pressureatmosphere.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the presentdisclosure, and together with the general description given above andthe detailed description of the embodiments given below, serve toexplain the principles of the present disclosure.

FIG. 1 is a diagram showing an example of a schematic overallconfiguration of a film forming system according to an embodiment.

FIG. 2 is a schematic sectional view of a first film forming apparatusaccording to an embodiment.

FIG. 3 is a schematic sectional view of a second film forming apparatusaccording to an embodiment.

FIG. 4 is a flowchart showing a flow of respective steps of a filmforming method according to an embodiment.

FIGS. 5A to 5D are sectional views schematically showing the states of awafer in the respective steps of the film forming method according to anembodiment.

FIG. 6 is a diagram showing a gas supply sequence at the time of formingan AlN film according to an embodiment.

FIG. 7 is a diagram showing a gas supply sequence at the time of forminga tungsten film according to an embodiment.

FIG. 8 is a diagram showing an example of a layer configuration of awafer according to the present embodiment.

FIG. 9 is a diagram showing an example of a layer configuration of awafer according to a comparative example.

FIG. 10 is a diagram showing an example of a change in resistivity withrespect to a thickness of a tungsten film.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments, examples ofwhich are illustrated in the accompanying drawings. In the followingdetailed description, numerous specific details are set forth in orderto provide a thorough understanding of the present disclosure. However,it will be apparent to one of ordinary skill in the art that the presentdisclosure may be practiced without these specific details. In otherinstances, well-known methods, procedures, systems, and components havenot been described in detail so as not to unnecessarily obscure aspectsof the various embodiments.

Hereinafter, embodiments of a tungsten film forming method and a filmforming system disclosed in the subject application will be described indetail with reference to the drawings. In the drawings, the same orcorresponding parts are designated by like reference numerals. Inaddition, the technique disclosed herein is not limited by theembodiments.

[System Configuration]

In the present embodiment, a case where film formation is performed by afilm forming system including a plurality of film forming apparatuseswill be described as an example. First, a film forming system accordingto the present embodiment will be described. FIG. 1 is a diagram showingan example of a schematic overall configuration of a film forming systemaccording to an embodiment. The film forming system 100 includes a firstfilm forming apparatus 101 and a second film forming apparatus 102. Inthe film forming system 100 according to the embodiment, the first filmforming apparatus 101 is used for forming an aluminum-containingmaterial film and the second film forming apparatus 102 is used forforming a tungsten film. A transfer mechanism (not shown) is connectedto the first film forming apparatus 101 and the second film formingapparatus 102, and a substrate as a film formation target is transferredby the transfer mechanism.

In the film forming system 100, a titanium nitride film (TiN) is formedas a base film, an aluminum-containing material film is formed on thetitanium nitride film (TiN), and then a tungsten film is formed on thealuminum-containing material film.

As shown in FIG. 1, the film forming system 100 includes one base filmforming apparatus 201 for forming a titanium nitride film (TiN), onefirst film forming apparatus 101 for forming an aluminum-containingmaterial film, and two second film forming apparatuses 102 for forming atungsten film. These apparatuses are connected to four wall portions ofa vacuum transfer chamber 301 having a heptagonal shape in a plan viewvia gate valves G, respectively. The inside of the vacuum transferchamber 301 is evacuated by a vacuum pump and kept at a predetermineddegree of vacuum. In other words, the film forming system 100 is amulti-chamber type vacuum processing system, in which a tungsten filmcan be continuously formed without breaking the vacuum. That is, all ofthe processes performed in the processing containers of the base filmforming apparatus 201, the first film forming apparatus 101, and thesecond film forming apparatuses 102 are performed without exposing asilicon wafer W (hereinafter referred to as “wafer W”) to the air.

The configurations of the first film forming apparatus 101 and thesecond film forming apparatus 102 will be described later. The base filmforming apparatus 201 is, for example, an apparatus for forming atitanium nitride film (TiN) by alternately supplying, for example, atitanium-containing gas and a nitrogen-containing gas onto the wafer Wby ALD (Atomic Layer Deposition) in a vacuum atmosphere chamber.

Three load lock chambers 302 are connected to the remaining three wallportions of the vacuum transfer chamber 301 via gate valves G1. At theopposite side of the vacuum transfer chamber 301 across the load lockchambers 302, an atmospheric transfer chamber 303 is provided. The threeload lock chambers 302 are connected to the atmospheric transfer chamber303 via gate valves G2. The load lock chambers 302 control a pressurebetween the atmospheric pressure and the vacuum when the wafer W istransferred between the atmospheric transfer chamber 303 and the vacuumtransfer chamber 301.

Three carrier attachment ports 305, to which carriers (FOUPs or thelike) C for accommodating wafers W are attached, are provided on thewall portion of the atmospheric transfer chamber 303 opposite to thewall portion to which the load lock chambers 302 are attached. Analignment chamber 304 for aligning the wafer W is provided on thesidewall of the atmospheric transfer chamber 303. A down-flow of cleanair is formed in the atmospheric transfer chamber 303.

Inside the vacuum transfer chamber 301, a transfer mechanism 306 isprovided. The transfer mechanism 306 transfers the wafer W to the basefilm forming apparatus 201, the first film forming apparatus 101, thesecond film forming apparatuses 102, and the load lock chambers 302. Thetransfer mechanism 306 has two independently-movable transfer arms 307 aand 307 b.

Inside the atmospheric transfer chamber 303, a transfer mechanism 308 isprovided. The transfer mechanism 308 is configured to transfer the waferW to the carriers C, the load lock chambers 302, and the alignmentchamber 304.

The film forming system 100 includes an overall control part 310. Theoverall control part 310 includes a main control part having a CPU(computer) for controlling the respective constituent parts of the basefilm forming apparatus 201, the first film forming apparatus 101 and thesecond film forming apparatus 102, the exhaust mechanism, the gas supplymechanism and the transfer mechanism 306 of the vacuum transfer chamber301, the exhaust mechanism and the gas supply mechanism of the load lockchamber 302, the transfer mechanism 308 of the atmospheric transferchamber 303, the drive systems of the gate valves G, G1 and G2, and thelike, an input device (a keyboard, a mouse, etc), an output device (aprinter, etc.), a display device (a display, etc.), and a storage device(a storage medium). The main control part of the overall control part310 causes the film forming system 100 to perform a predeterminedoperation, for example, based on a processing recipe stored in a storagemedium built in the storage device or in a storage medium set in thestorage device. The overall control part 310 may be a higher-levelcontrol part of the control parts of the respective units, such as thecontrol part 6 of the first film forming apparatus 101 and the secondfilm forming apparatus 102 which will be described later.

Next, the operation of the film forming system 100 configured asdescribed above will be described. The following processing operation isexecuted based on the processing recipe stored in the storage medium inthe overall control part 310.

First, the wafer W is taken out from the carrier C connected to theatmospheric transfer chamber 303 by the transfer mechanism 308. Afterpassing through the alignment chamber 304, the wafer W is loaded intoone of the lock chambers 302 by opening the gate valve G2 of one of theload lock chambers 302. After closing the gate valve G2, the inside ofthe load lock chamber 302 is evacuated.

When the load lock chamber 302 reaches a predetermined degree of vacuum,the gate valve G1 is opened to take out the wafer W from the load lockchamber 302 by one of the transfer arms 307 a and 307 b of the transfermechanism 306.

Then, the gate valve G of the base film forming apparatus 201 is opened,the wafer W held by one of the transfer arms of the transfer mechanism306 is loaded into the base film forming apparatus 201, and the emptytransfer arm is returned to the vacuum transfer chamber 301. The gatevalve G is closed, and a film forming process of a titanium nitride film(TiN) is performed by the base film forming apparatus 201.

After completion of the film forming process of the titanium nitridefilm (TiN), the gate valve G of the base film forming apparatus 201 isopened and the wafer W therein is unloaded by one of the transfer arms307 a and 307 b of the transfer mechanism 306. Then, the gate valve G ofthe first film forming apparatus 101 is opened, the wafer W held by thetransfer arm is loaded into the first film forming apparatus 101, andthe empty transfer arm is returned to the vacuum transfer chamber 301.The valve G is closed, and a film forming process of analuminum-containing material film is performed by the first film formingapparatus 101 on the titanium nitride film (TiN) formed on the wafer W.

After completion of the film forming process of the aluminum-containingmaterial film, the gate valve G of the first film firming apparatus 101is opened and the wafer W therein is unloaded by one of the transferarms 307 a and 307 b of the transfer mechanism 306. Then, the gate valveG of the second film forming apparatus 102 is opened, the wafer W heldby the transfer arm is loaded into the second film forming apparatus102, and the empty transfer arm is returned to the vacuum transferchamber 301. The gate valve G is closed, and a film forming process of atungsten film is performed by the second film forming apparatus 102 onthe aluminum-containing material film formed on the wafer W.

After the tungsten film is formed in this manner, the gate valve G ofthe second film forming apparatus 102 is opened and the wafer W thereinis unloaded by one of the transfer arms 307 a and 307 b of the transfermechanism 306. Then, the gate valve G1 of one of the load lock chambers302 is opened, and the wafer W held on the transfer arm is loaded intothe load lock chamber 302. Then, the inside of the load lock chamber 302is returned to the atmosphere, the gate valve G2 is opened, and thewafer W in the load lock chamber 302 is returned to the carrier C by thetransfer mechanism 308.

The above processes are performed concurrently on a plurality of wafersW, whereby the film forming process of the tungsten film for apredetermined number of wafers W is completed.

As described above, the film forming system 100 is formed by mountingone base film forming apparatus 201, one first film forming apparatus101, and two second film forming apparatuses 102. This makes it possibleto realize the formation of the titanium nitride film (TiN), theformation of the aluminum-containing material film, and the formation ofthe tungsten film with high throughput. Although the film forming system100 of the present embodiment is shown as a vacuum processing systemmounted with four film forming apparatuses, the number of film formingapparatuses is not limited thereto as long as the vacuum processingsystem is capable of mounting a plurality of film forming apparatuses.The number of film forming apparatuses may be four or more. For example,a vacuum processing system mounted with eight or more film formingapparatuses may be used.

[Configuration of Film Forming Apparatus]

The first film forming apparatus 101 and the second film formingapparatus 102 have substantially the same configuration. Hereinafter,the configuration of the first film forming apparatus 101 will be mainlydescribed. As for the configuration of the second film forming apparatus102, different parts will be mainly described.

The configuration of the first film forming apparatus 101 will bedescribed. FIG. 2 is a schematic sectional view of the first filmforming apparatus according to an embodiment. The first film formingapparatus 101 includes a processing container 1, a mounting table 2, ashower head 3, an exhaust part 4, a gas supply mechanism 5, and acontrol part 6.

The processing container 1 is made of a metal such as aluminum or thelike and has a substantially cylindrical shape. The processing container1 accommodates a wafer W as a substrate to be processed. Aloading/unloading port 11 for loading or unloading the wafer W is formedon the side wall of the processing container 1. The loading/unloadingport 11 is opened and closed by a gate valve 12. An annular exhaust duct13 having a rectangular cross section is provided on the main body ofthe processing container 1. A slit 13 a is formed in the exhaust duct 13along the inner peripheral surface. An exhaust port 13 b is formed inthe outer wall of the exhaust duct 13. On the upper surface of theexhaust duct 13, a top wall 14 is provided so as to close the upperopening of the processing container 1. The space between the exhaustduct 13 and the top wall 14 is hermetically sealed by a seal ring 15.

The mounting table 2 horizontally supports the wafer W in the processingcontainer 1. The mounting table 2 is formed in a disk shape having asize corresponding to the wafer W and is supported by a support member23. The mounting table 2 is made of a ceramic material such as aluminumnitride (AlN) or the like, or a metallic material such as aluminum,nickel alloy, or the like. A heater 21 for heating the wafer W is buriedin the mounting table 2. The heater 21 is supplied with electric powerfrom a heater power supply (not shown) to generate heat. Then, theoutput of the heater 21 is controlled by a temperature signal of athermocouple (not shown) provided in the vicinity of the upper surfaceof the mounting table 2, whereby the wafer W is controlled to apredetermined temperature. In the mounting table 2, a cover member 22formed of ceramics such as alumina or the like is provided so as tocover the outer peripheral region of the upper surface and the sidesurface.

On the bottom surface of the mounting table 2, a support member 23 forsupporting the mounting table 2 is provided. The support member 23extends downward from the center of the bottom surface of the mountingtable 2 through a hole formed in the bottom wall of the processingcontainer 1. The lower end of the support member 23 is connected to anelevating mechanism 24. The mounting table 2 is raised and lowered viathe support member 23 by the elevating mechanism 24 between a processingposition shown in FIG. 2 and a transfer position located below theprocessing position as indicated by a two-dot chain line so that thewafer W can be transferred. A flange portion 25 is attached to thesupport member 23 on the lower side of the processing container 1.Between the bottom surface of the processing container 1 and the flangeportion 25, there is provided a bellows 26 which isolates the atmosphereinside the processing container 1 from external air and which expandsand contracts in response to the upward/downward movement of themounting table 2.

Three wafer support pins 27 (only two of which are shown) are providedin the vicinity of the bottom surface of the processing container 1 soas to protrude upward from an elevating plate 27 a. The wafer supportpins 27 are raised and lowered via the elevating plate 27 a by anelevating mechanism 28 provided below the processing container 1. Thewafer support pins 27 are inserted through the through holes 2 aprovided in the mounting table 2 located at the transfer position andcan protrude and retract with respect to the upper surface of themounting table 2. By moving the wafer support pins 27 up and down, thedelivery of the wafer W between the transfer mechanism (not shown) andthe muffling table 2 is performed.

The shower head 3 supplies a processing gas into the processingcontainer 1 in a shower shape. The shower head 3 is made of a metal andis provided so as to face the mounting table 2. The shower head 3 hassubstantially the same diameter as the mounting table 2. The shower head3 includes a main body portion 31 fixed to the top wall 14 of theprocessing container 1 and a shower plate 32 connected to a lowerportion of the main body portion 31. A gas diffusion space 33 is formedbetween the main body portion 31 and the shower plate 32. In the gasdiffusion space 33, gas introduction holes 36 and 37 are provided so asto penetrate the top wall 14 of the processing container 1 and thecenter of the main body portion 31. An annular protrusion 34 protrudingdownward is formed in the peripheral edge portion of the shower plate32. Gas discharge holes 35 are formed on the inner flat surface of theannular protrusion 34. In a state in which the mounting table 2 islocated at the processing position, a processing space 38 is formedbetween the mounting table 2 and the shower plate 32, and the uppersurface of the cover member 22 and the annular protrusion 34 come closeto each other to form an annular gap 39.

The exhaust part 4 evacuates the inside of the processing container 1.The exhaust part 4 includes an exhaust pipe 41 connected to the exhaustport 13 b and an exhaust mechanism 42 having a vacuum pump, a pressurecontrol valve, and the like connected to the exhaust pipe 41. In aprocess, the gas in the processing container 1 is moved to the exhaustduct 13 via the slit 13 a and is exhausted from the exhaust duct 13through the exhaust pipe 41 by the exhaust mechanism 42.

The gas supply mechanism 5 is connected to the gas introduction holes 36and 37 and is capable of supplying various gases used for filmformation. For example, the gas supply mechanism 5 includes anAl-containing gas supply source 51 a, an N₂ gas supply source 53 a, anNH₃ gas supply source 55 a, and an N₂ gas supply source 57 a, whichserve as gas supply sources for forming a film of an aluminum-containingmaterial. In the gas supply mechanism 5 shown in FIG. 2, the respectivegas supply sources are shown separately. However, gas supply sourcescapable of being used in common may be used in common.

The Al-containing gas supply source 51 a supplies an Al-containing gasinto the processing container 1 via a gas supply line 51 b. Examples ofthe Al-containing gas include an AlCl₃ gas and a TMA (trimethylaluminum:C₆H₁₈Al₂) gas. In the gas supply line 51 b, a flow rate controller 51 c,a storage tank 51 d, and a valve 51 e are installed sequentially fromthe upstream side. On the downstream side of the valve 51 e, the gassupply line 51 b is connected to the gas introduction hole 36. TheAl-containing gas supplied from the Al-containing gas supply source 51 ais temporarily stored in the storage tank 51 d before being suppliedinto the processing container 1, pressurized to a predetermined pressurein the storage tank 51 d, and then supplied to the processing container1. The supply and cutoff of the Al-containing gas to be supplied fromthe storage tank 51 d to the processing container 1 is performed by thevalve 51 e. By temporarily storing the Al-containing gas in the storagetank 51 d in this manner, the Al-containing gas can be stably suppliedinto the processing container 1 at a relatively large flow rate.

The N₂ gas supply source 53 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 53 b. In the gas supplyline 53 b, a flow rate controller 53 c, a valve 53 e, and an orifice 53f are installed sequentially from the upstream side. On the downstreamside of the orifice 53 f, the gas supply line 53 b is connected to thegas supply line 51 b. The N₂ gas supplied from the N₂ gas supply source53 a is continuously supplied into the processing container 1 during thefilm formation on the wafer W. The supply and cutoff of the N₂ gas to besupplied from the N₂ gas supply source 53 a to the processing container1 are performed by the valve 53 e. The gas is supplied to the gas supplyline 51 b at a relatively large flow rate by the storage tank 51 d. Thegas supplied to the gas supply line 51 b is prevented from flowing backto the gas supply line 53 b by the orifice 53 f.

The NH₃ gas supply source 55 a supplies an NH₃ gas as a reducing gasinto the processing container 1 via a gas supply line 55 b. In the gassupply line 55 b, a flow rate controller 55 c, a storage tank 55 d, anda valve 55 e are installed sequentially from the upstream side. On thedownstream side of the valve 55 e, the gas supply line 55 b is connectedto the gas supply line 54 b. The downstream side of the gas supply line54 b is connected to the gas introduction hole 37. An NH₃ gas suppliedfrom the NH₃ gas supply source 55 a is temporarily stored in the storagetank 55 d before being supplied into the processing container 1,pressurized to a predetermined pressure in the storage tank 55 d, andthen introduced into the processing container 1. The supply and cutoffof the NH₃ gas to be supplied from the storage tank 55 d to theprocessing container 1 are performed by the valve 55 e. By temporarilystoring the NH₃ gas in the storage tank 55 d in this manner, the NH₃ gascan be stably supplied into the processing container 1 at a relativelylarge flow rate.

The N₂ as supply source 57 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 57 b. In the gas supplyline 57 b, a flow rate controller 57 c, a valve 57 e, and an orifice 57f are installed sequentially from the upstream side. On the downstreamside of the orifice 57 f, the gas supply line 57 b is connected to thegas supply line 54 b. The N₂ gas supplied from the N₂ gas supply source57 a is continuously supplied into the processing container 1 during thefilm formation on the wafer W. The supply and cutoff of the N₂ gas to besupplied from the N₂ gas supply source 57 a to the processing container1 are performed by the valve 57 e. The gas is supplied to the gas supplyline 55 b at a relatively large flow rate by the storage tank 55 d. Thegas supplied to the gas supply line 55 b is prevented from flowing backto the gas supply line 57 b by the orifice 57 f.

The operation of the first film forming apparatus 101 configured asdescribed above is generally controlled by the control part 6. Thecontrol part 6 is, for example, a computer, and includes a CPU (CentralProcessing Unit), a RAM (Random Access Memory), a ROM (Read OnlyMemory), an auxiliary storage device, and the like. The CPU operatesbased on a program stored in the ROM or the auxiliary storage device,and controls the overall operation of the apparatus. The control part 6may be provided inside the first film forming apparatus 101 or may beprovided outside the first film forming apparatus 101. When the controlpart 6 is provided outside the first film forming apparatus 101, thecontrol part 6 can control the first film forming apparatus 101 by awired or wireless communication means.

Next, the configuration of the second film forming apparatus 102 will bedescribed. FIG. 3 is a schematic sectional view of the second filmforming apparatus 102 according to the embodiment. The second filmforming apparatus 102 has the same configuration as the first filmforming apparatus 101 except for the gas to be used and the gas supplymechanism 5 for supplying the gas. The parts of the second film formingapparatus 102 which are the same as those of the first film formingapparatus 101 are denoted by like reference numerals, and a descriptionthereof will be omitted. Different points will be mainly described.

The gas supply mechanism 5 is connected to gas introduction holes 36 and37, and is capable of supplying various gases used for film formation.For example, the gas supply mechanism 5 includes a WF₆ gas supply source61 a, an N₂ gas supply source 62 a, an N₂ gas supply source 63 a, an H₂gas supply source 64 a, an H₂ gas supply source 65 a, an N₂ gas supplysource 66 a, and an N₂ gas supply source 67 a. Even in the gas supplymechanism 5 shown in FIG. 3, the respective gas supply sources areseparately shown. However, the gas supply sources capable of being usedin common may be used in common.

The WF₆ gas supply source 61 a supplies a WF₆ gas into the processingcontainer 1 via a gas supply line 61 b. In the gas supply line 61 b, aflow rate controller 61 c, a storage tank 61 d, and a valve 61 e areinstalled sequentially from the upstream side. On the downstream side ofthe valve 61 e, the gas supply line 61 b is connected to the gasintroduction hole 36. The WF₆ gas supplied from the WF₆ gas supplysource 61 a is temporarily stored in the storage tank 61 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 61 d, and then supplied into the processingcontainer 1. The supply and cutoff of the WF₆ gas to be supplied fromthe storage tank 61 d to the processing container 1 is performed by thevalve 61 e. By temporarily storing the WF₆ gas in the storage tank 61 din this manner, the WF₆ gas can be stably supplied into the processingcontainer 1 at a relatively large flow rate.

The N₂ gas supply source 62 a supplies an N₂ gas as a purge gas into theprocessing container 1 via a gas supply line 62 b. In the gas supplyline 62 b, a flow rate controller 62 c, a storage tank 62 d, and a valve62 e are installed sequentially from the upstream side. On thedownstream side of the valve 62 e, the gas supply line 62 b is connectedto the gas supply line 61 b. The N₂ gas supplied from the N₂ gas supplysource 62 a is temporarily stored in the storage tank 62 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 62 d, and then supplied into the processingcontainer 1. The supply and cutoff of the N₂ gas to be supplied from thestorage tank 62 d to the processing container 1 is performed by thevalve 62 e. By temporarily storing the N₂ gas in the storage tank 62 din this manner, the N₂ gas can be stably supplied into the processingcontainer 1 at a relatively large flow rate.

The N₂ gas supply source 63 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 63 b. In the gas supplyline 63 b, a flow rate controller 63 c, a valve 63 e, and an orifice 63f are installed sequentially from the upstream side. On the downstreamside of the orifice 63 f, the gas supply line 63 b is connected to thegas supply line 61 b. The N₂ gas supplied from the N₂ gas supply source63 a is continuously supplied into the processing container 1 during thefilm formation on the wafer W. The supply and cutoff of the N₂ gas to besupplied from the N₂ gas supply source 63 a to the processing container1 are performed by the valve 63 e. The gas is supplied to the gas supplylines 61 b and 62 b at a relatively large flow rate by the storage tanks61 d and 62 d. The gas supplied to the gas supply lines 61 b and 62 b isprevented from flowing back to the gas supply line 63 b by the orifice63 f.

The H₂ gas supply source 64 a supplies an H₂ gas as a reducing gas intothe processing container 1 via a gas supply line 64 b. In the gas supplyline 64 b, a flow rate controller 64 c, a valve 64 e, and an orifice 64f are installed sequentially from the upstream side. On the downstreamside of the orifice 64 f, the gas supply line 64 b is connected to thegas introduction hole 37. The H₂ gas supplied from the H₂ gas supplysource 64 a is continuously supplied into the processing container 1during the film formation on the wafer W. The supply and cutoff of theH₂ gas to be supplied from the H₂ gas supply source 64 a to theprocessing container 1 are performed by the valve 64 e. The gas issupplied to the gas supply lines 65 b and 66 b at a relatively largeflow rate by the storage tanks 65 d and 66 d which will be describedlater. The gas supplied to the gas supply lines 65 b and 66 b isprevented from flowing back into the gas supply line 64 b by the orifice64 f.

The H₂ gas supply source 65 a supplies an H₂ gas as a reducing gas intothe processing container 1 via a gas supply line 65 b. In the gas supplyline 65 b, a flow rate controller 65 c, a storage tank 65 d, and a valve65 e are installed sequentially from the upstream side. On thedownstream side of the valve 65 e, the gas supply line 65 b is connectedto the gas supply line 64 b. The H₂ gas supplied from the H₂ gas supplysource 65 a is temporarily stored in the storage tank 65 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 65 d, and then supplied into the processingcontainer 1. The supply and cutoff of the H₂ gas to be supplied from thestorage tank 65 d to the processing container 1 is performed by thevalve 65 e. By temporarily storing the H₂ gas in the storage tank 65 din this manner, the H₂ gas can be stably supplied into the processingcontainer 1 at a relatively large flow rate.

The N₂ gas supply source 66 a supplies an N₂ gas as a purge gas into theprocessing container 1 via a gas supply line 66 b. In the gas supplyline 66 b, a flow rate controller 66 c, a storage tank 66 d, and a valve66 e are installed sequentially from the upstream side. On thedownstream side of the valve 66 e, the gas supply line 66 b is connectedto the gas supply line 64 b. The N₂ gas supplied from the N₂ gas supplysource 66 a is temporarily stored in the storage tank 66 d before beingsupplied into the processing container 1, pressurized to a predeterminedpressure in the storage tank 66 d, and then supplied into the processingcontainer 1. The supply and cutoff of the N₂ gas to be supplied from thestorage tank 66 d to the processing container 1 are performed by thevalve 66 e. By temporarily storing the N₂ gas in the storage tank 66 din this manner, the N₂ gas can be stably supplied into the processingcontainer 1 at a relatively large flow rate.

The N₂ gas supply source 67 a supplies an N₂ gas as a carrier gas intothe processing container 1 via a gas supply line 67 b. In the gas supplyline 67 b, a flow rate controller 67 c, a valve 67 e, and an orifice 67f are installed sequentially from the upstream side. On the downstreamside of the orifice 67 f, the gas supply line 67 b is connected to thegas supply line 64 b. The N₂ gas supplied from the N₂ gas supply source67 a is continuously supplied into the processing container 1 during thefilm formation on the wafer W. The supply and cutoff of the N₂ gas to besupplied from the N₂ gas supply source 67 a to the processing container1 are performed by the valve 67 e. The gas is supplied to the gas supplylines 65 b and 66 b at a relatively large flow rate by the storage tanks65 d and 66 d. The gas supplied to the gas supply lines 65 b and 66 b isprevented from flowing back to the gas supply line 67 b by the orifice67 f.

[Film Forming Method]

Next, a tungsten film forming method, which is performed using theforming system 100 configured as described above, will be described.FIG. 4 is a flowchart showing the flow of respective steps of a filmforming method according to an embodiment. FIGS. 5A to 5D are sectionalviews schematically showing the states of a wafer in the respectivesteps of the film forming method according to the embodiment.

First, in the film forming method according to the present embodiment, awafer W (FIG. 5A) having a titanium nitride (TiN) film as a base filmformed on the surface of a silicon film having a recess such as, forexample, a trench or a hole, is prepared. In reality, a recess such as atrench or a hole (a contact hole or via hole) is formed in the wafer W.However, for the sake of convenience, the recess is omitted in FIGS. 5Ato 5D.

The first film forming apparatus 101 forms a film of analuminum-containing material on the wafer W by an ALD (Atomic LayerDeposition) method (step S1: FIG. 5B). For example, in the first filmforming apparatus 101, an Al-containing gas and a reducing gas aresupplied into the processing container 1 to form an AlN film as a filmof an aluminum-containing material. Details of the step of forming theAlN film will be described later.

The second film forming apparatus 102 supplies a WF₆ gas and an SiH₄ gasinto the processing container 1 to form a nucleation film as an initialtungsten film for generating tungsten nuclei on the surface of the waferW (step S2: FIG. 5C). Step S3 is a process for facilitating theformation of the next tungsten film, but is not necessarily required.The step S3 may be a step in which the second film forming apparatus 102treats the surface of the wafer W by supplying an SiH₄ gas into theprocessing container 1 for a predetermined time.

Next, the second film forming apparatus 102 forms a tungsten film on thewafer W (step S3: FIG. 5D). Details of the step of forming the tungstenfilm will be described later.

[Formation of AlN Film]

Next, a flow of forming an AlN film by the first film forming apparatus101 will be described. FIG. 6 is a diagram showing a gas supply sequenceat the time of forming the AlN film according to the embodiment.

The control part 6 of the first film forming apparatus 101 controls theheater 21 of the mounting table 2 to heat the wafer W to a predeterminedtemperature (for example, 250 to 650 degrees C.). Further, the controlpart 6 controls the pressure control valve of the exhaust mechanism 42to adjust the pressure in the processing container 1 to a predeterminedpressure (for example, 1.3×10¹ to 8.0×10³ Pa).

The control part 6 opens the valves 53 e and 57 e and supplies a carriergas (N₂ gas) at a predetermined flow rate (for example, 100 to 10000sccm) from the N₂ gas supply sources 53 a and 57 a to the gas supplylines 53 b and 57 b, respectively. In addition, the control part 6supplies an Al-containing gas and an NH₃ gas from the Al-containing gassupply source 51 a and the NH₃ gas supply source 55 a to the gas supplylines 51 b and 55 b, respectively. At this time, since the valves 51 eand 55 e are closed, the Al-containing gas and the NH₃ gas arerespectively stored in the storage tanks 51 d and 55 d, and the pressurein the storage tanks 51 d and 55 d is increased.

Next, the control part 6 opens the valve 51 e, supplies theAl-containing gas stored in the storage tank 51 d into the processingcontainer 1, and causes the film of the aluminum-containing material tobe adsorbed on the surface of the wafer W (step S11). For example, whenan AlCl₃ gas is used as the Al-containing gas, the AlCl₃ gas goesthrough a reaction of AlCl₃+NH₃→AlN+HCl ⬆ and AlN adsorbs on the surfaceof the wafer W. Moreover, for example, when a TMA gas is used as theAl-containing gas, the TMA gas goes through a reaction ofC₆H₁₈Al₂+NH₃→AlN+C_(x)H_(y) ⬆, and AlN adsorbs on the surface of thewafer W.

After a predetermined time (for example, 0.05 to 5 seconds) has elapsedsince the opening of the valve 51 e, the control part 6 closes the valve51 e and stops the supply of the Al-containing gas into the processingcontainer 1 (step S12). As the valve 51 e is closed, the Al-containinggas supplied from the Al-containing gas supply source 51 a to the gassupply line 51 b is stored in the storage tank 51 d, and the pressure inthe storage tank 51 d is increased. In addition, since the valve 51 e isclosed, the carrier gas (N₂) supplied from the gas supply line 53 b andthe gas supply line 57 b may also function as a purge gas to exhaust anexcess Al-containing gas (step S12).

After a predetermined time (for example, 0.05 to 5 seconds) has elapsedsince the closing of the valve 51 e, the control part 6 opens the valve55 e and supplies the NH₃ gas stored in the storage tank 55 d into theprocessing container 1, thereby reducing the Al-containing gas adsorbedon the surface of the wafer W (step S13).

After a predetermined time (for example, 0.05 to 5 seconds) has elapsedsince the opening of the valve 55 e, the control part 6 closes the valve55 e and stops the supply of the NH₃ gas into the processing container 1(step S14). As the valve 55 e is closed, the NH₃ gas supplied from theNH₃ gas supply source 55 a to the gas supply line 55 b is stored in thestorage tank 55 d, and the pressure in the storage tank 55 d isincreased. In addition, as the valve 51 e is closed, the carrier gas(N₂) supplied from the gas supply line 53 b and the gas supply line 57 bmay also function as a purge gas to exhaust an excess Al-containing gas(step S14).

The control part 6 forms an AlN film having a desired film thickness byrepeating the cycle of steps S11 to S14 for a plurality of cycles (forexample, 10 to 1000 cycles).

The gas supply sequence and the process gas conditions at the time offorming the AlN film shown in FIG. 6 are merely examples, and thepresent disclosure is not limited thereto. The AlN film may be formed byusing other gas supply sequences and other process gas conditions.

[Formation of Tungsten Film]

Next, a flow of forming a tungsten film by the second film formingapparatus 102 will be described. FIG. 7 is a diagram showing a gassupply sequence at the time of forming a tungsten film according to anembodiment.

The control part 6 of the second film forming apparatus 102 controls theheater 21 of the mounting table 2 to heat the wafer W to a predeterminedtemperature (for example, 250 to 650 degrees C.). Further, the controlpart 6 controls the pressure control valve of the exhaust mechanism 42to adjust the pressure in the processing container 1 to a predeterminedpressure (for example, 1.3×10¹ to 8.0×10³ Pa).

The control part 6 opens the valves 63 e and 67 e and supplies a carriergas (N₂ gas) at a predetermined flow rate (for example, 100 to 8000sccm) from the N₂ gas supply sources 63 a and 67 a to the gas supplylines 63 b and 67 b, respectively. Further, the control part 6 opens thevalve 64 e and supplies an H₂ gas at a predetermined flow rate (forexample, 100 to 20000 sccm) from the H₂ gas supply source 64 a to thegas supply line 64 b. Moreover, the control part 6 supplies a WF₆ gasand an H₂ gas from the WF₆ gas supply source 61 a and the H₂ gas supplysource 65 a, respectively, to the gas supply lines 61 b and 65 b. Atthis time, since the valves 61 e and 65 e are closed, the WF₆ gas andthe H₂ gas are respectively stored in the storage tanks 61 d and 65 d,and the pressure in the storage tanks 61 d and 65 d is increased.

Next, the control part 6 opens the valve 61 e, supplies the WF₆ gasstored in the storage tank 61 d into the processing container 1, andcauses the WF₆ gas to be adsorbed on the surface of the wafer W (stepS21). In parallel with the supply of the WF₆ gas into the processingcontainer 1, the control part 6 supplies a purge gas (N₂ gas) from theN₂ gas supply sources 62 a and 66 a to the gas supply lines 62 b and 66b, respectively. At this time, by closing the valves 62 e and 66 e, thepurge gas is stored in the storage tanks 62 d and 66 d, and the pressurein the storage tanks 62 d and 66 d is increased.

After a predetermined time (for example, 0.05 to 5 seconds) has elapsedsince the opening of the valve 61 e, the control part 6 closes the valve61 e and opens the valves 62 e and 66 e to stop the supply of the WF₆gas into the processing container 1 and to supply the purge gas storedin the storage tanks 62 d and 66 d into the processing container 1 (stepS22). At this time, the purge gas is supplied from the storage tanks 62d and 66 d having an increased pressure. Therefore, the purge gas issupplied into the processing container 1 at a relatively large flowrate, for example, a flow rate (for example, 500 to 10000 sccm) largerthan the flow rate of the carrier gas. Thus, the WF₆ gas remaining inthe processing container 1 is promptly discharged to the exhaust pipe41, and the inside of the processing container 1 is changed from the WF₆gas atmosphere to the atmosphere containing the H₂ gas and the N₂ gas ina short time. On the other hand, as the valve 61 e is closed, the WF₆gas supplied from the WF₆ gas supply source 61 a to the gas supply line61 b is stored in the storage tank 61 d, and the pressure in the storagetank 61 d is increased.

After a predetermined time (for example, 0.05 to 5 seconds) has elapsedsince the opening of the valves 62 e and 66 e, the control part 6 closesthe valves 62 e and 66 e and opens the valve 65 e to stop the supply ofthe purge gas into the processing container 1 and to supply the H₂ gasstored in the storage tank 65 d into the processing container 1, therebyreducing the WF₆ gas adsorbed on the surface of the wafer W (step S23).At this time, due to the closing of the valves 62 e and 66 e, the purgegas supplied from the N₂ gas supply sources 62 a and 66 a to the gassupply lines 62 b and 66 b, respectively, is stored in the storage tanks62 d and 66 d, and the pressure in the storage tanks 62 d and 66 d isincreased.

After a predetermined time (for example, 0.05 to 5 seconds) has elapsedsince the opening of the valve 65 e, the control part 6 closes the valve65 e and opens the valves 62 e and 66 e to stop the supply of the H₂ gasinto the processing container 1 and to supply the purge gas stored inthe storage tanks 62 d and 66 d into the processing container 1 (stepS24). At this time, the purge gas is supplied from the storage tanks 62d and 66 d having an increased pressure. Therefore, the purge gas issupplied into the processing container 1 at a relatively large flowrate, for example, a flow rate (for example, 500 to 10000 sccm) largerthan the flow rate of the carrier gas. Thus, the H₂ gas remaining in theprocessing container 1 is promptly discharged to the exhaust pipe 41,and the inside of the processing container 1 is changed from the H₂ gasatmosphere to the atmosphere containing the H₂ gas and the N₂ gas in ashort time. On the other hand, due to the closing of the valve 65 e, theH₂ gas supplied from the H₂ gas supply source 65 a to the gas supplyline 65 b is stored in the storage tank 65 d, and the pressure in thestorage tank 65 d is increased.

The control part 6 forms a tungsten film having a desired film thicknessby repeating the cycle of steps S21 to S24 for a plurality of cycles(for example, 50 to 2000 cycles).

The gas supply sequence and the process gas conditions at the time offorming the tungsten film shown in FIG. 7 are merely examples, and thepresent disclosure is not limited thereto. The tungsten film may beformed by using other gas supply sequences and other process gasconditions.

[Action and Effect]

Next, the actions and effects of the film forming method according tothe present embodiment will be described. FIG. 8 is a diagram showing anexample of the layer configuration of the wafer according to the presentembodiment. FIG. 8 shows an example of the layer configuration of thewafer W on which films are formed by the film forming method accordingto the present embodiment. In the wafer W, an AlO layer for blocking isformed on a silicon (SiO₂) layer, and a TiN film having a thickness of,for example, 1 nm is formed on the AlO layer from the viewpoint ofadhesion and reaction suppression. Then, in the wafer W, an AlN filmhaving a thickness of, for example, 1 nm is formed on the TiN film bythe film forming method according to the present embodiment, and anucleation film (Nuc) having a thickness of, for example, 1 nm is formedas an initial tungsten film on the AlN film. Then, in the wafer W, alow-resistance tungsten film (W) is formed on the nucleation film.

One example of the process conditions of the film forming methodaccording to the embodiment will now be summarized below.

AlN Film

-   Temperature: 250 to 550 degrees C.-   Pressure: 0.1 to 10 Torr-   Al-containing gas: 10 to 500 sccm-   Carrier gas (N₂): 1000 to 10000 sccm-   Purge gas (N₂): 0 to 10000 sccm-   NH₃ gas: 1000 to 10000 sccm-   Time:-   Al-containing gas: 0.05 to 5 seconds-   Purge: 0.05 to 5 seconds-   NH₃ gas: 0.05 to 5 seconds-   Purge: 0.05 to 5 seconds

Nucleation Film

-   Temperature: 250 to 550 degrees C.-   Pressure: 1 to 100 Torr-   W-containing gas: 10 to 500 sccm-   Carrier gas (N₂): 1000 to 10000 sccm-   Purge gas (N₂): 0 to 10000 sccm-   H₂ gas: 500 to 20000 sccm-   SiH₄ gas: 10 to 1000 sccm-   Time:-   W-containing gas: 0.05 to 15 seconds-   Purge: 0.05 to 15 seconds-   SiH₄ gas: 0.05 to 15 seconds-   Purge: 0.05 to 15 seconds

W Film

-   Temperature: 250 to 550 degrees C.-   Pressure: 0.1 to 20 Torr-   W-containing gas: 100 to 500 sccm-   Carrier gas (N₂): 1000 to 10000 sccm-   Purge gas (N₂): 0 to 10000 sccm-   H₂ gas: 500 to 20000 sccm-   Time:-   W-containing gas: 0.05 to 15 seconds-   Purge: 0.05 to 15 seconds-   H₂ gas: 0.05 to 15 seconds-   Purge: 0.05 to 15 seconds

In the wafer W, by forming the AlN film on the TiN film before formingthe tungsten film as described above, the AlN film can cancel theorientation of TiN. The AlN film preferably has a thickness of about 1to 2 nm. If the thickness is about 1 nm, it is possible to cancel theorientation of the underlying TiN. As a result, in the wafer W, grainsof tungsten to be deposited can be caused to grow into a larger size andthe resistance of the tungsten film can be reduced.

Furthermore, in the wafer W, by forming the nucleation film, it ispossible to enhance the adhesion of tungsten to be deposited. Inaddition, it is possible to enhance the uniformity of tungsten to bedeposited. The thickness of the nucleation film is preferably about 0.5to 5 nm.

The effects will be described using a comparative example. FIG. 9 is adiagram showing an example of a layer configuration of a wafer accordingto a comparative example. FIG. 9 shows an example of a layerconfiguration of a conventional wafer W. In the wafer W, an AlO layerfor blocking is formed on a silicon (SiO₂) layer, and a TiN film havinga thickness of, for example, 2 nm is formed on the AlO layer from theviewpoint of adhesion and reaction suppression. Then, in the wafer W, atungsten nucleation film (Nuc) having a thickness of, for example, 3 nmis formed on the TiN film. Then, in the wafer W, a low-resistancetungsten film (W) is formed on the nucleation film.

An example of the process conditions for forming each film of thecomparative example will be described below.

Nucleation Film

-   Temperature: 250 to 550 degrees C.-   Pressure: 1 to 100 Torr-   W-containing gas: 10 to 500 sccm-   Carrier gas (N₂): 1000 to 10000 sccm-   Purge gas (N₂): 0 to 10000 sccm-   H₂ gas: 500 to 20000 sccm-   SiH₄ gas: 10 to 1000 sccm-   Time:-   W-containing gas: 0.05 to 15 seconds-   Purge: 0.05 to 15 seconds-   SiH₄ gas: 0.05 to 15 seconds-   Purge: 0.05 to 15 seconds

W Film

-   Temperature: 250 to 550 degrees C.-   Pressure: 0.1 to 20 Torr-   W-containing gas: 100 to 500 sccm-   Carrier gas (N₂): 1000 to 10000 sccm-   Purge gas (N₂): 0 to 10000 sccm-   H₂ gas: 500 to 20000 sccm-   Time:-   W-containing gas: 0.05 to 15 seconds-   Purge: 0.05 to 15 seconds-   H₂ gas: 0.05 to 15 seconds-   Purge: 0.05 to 15 seconds

FIG. 10 is a diagram showing an example of a change in resistivity withrespect to the thickness of the tungsten film. FIG. 10 shows a change inresistivity depending on the thickness of the tungsten film in the layerconfiguration of the present embodiment shown in FIG. 8 and the layerconfiguration of the comparative example shown in FIG. 9. In the exampleof FIG. 10, the thickness of the tungsten film is measured from theinterface with the TiN film. That is, in the layer configuration of thepresent embodiment, the thickness of the AlN film, the nucleation film(Nuc), and the tungsten film (W) is regarded as the thickness of thetungsten film. In the layer configuration of the comparative example,the thickness of the nucleation film (Nuc) and the tungsten film (W) isregarded as the thickness of the tungsten film. In the example of FIG.10, there is shown the resistivity normalized with reference to theresistivity of the comparative example when the thickness is 10 nm. Asshown in FIG. 10, when the thickness is 10 nm, the resistivity of thelayer configuration of the present embodiment is lower by 59% than thatof the comparative example. When the thickness is 15 nm, the resistivityof the layer configuration of the present embodiment is lower by 41%than that of the comparative example.

As described earlier, the wiring of the LSI is miniaturized, and thereduction in the resistance of the wiring is required. For example, in athree-dimensional stacked semiconductor memory such as a 3D NAND flashmemory or the like, a tungsten film is formed as a word line. Forpurposes of miniaturization, it is required to further reduce theresistance of the tungsten film.

On the other hand, in the layer configuration of the present embodiment,it is possible to reduce the resistance of the tungsten film even whenthe film thickness is made small.

Conventionally, when forming a nucleation film, a boron (B₂H₆) gas isused as a reducing gas. However, boron may adversely affect the wafer Win some cases.

On the other hand, when forming the nucleation film according to thepresent embodiment, an adverse effect can be suppressed by using theSiH₄ gas as a reducing gas.

In the layer configuration of the present embodiment shown FIG. 8, thereis shown a case where the nucleation film is provided. However, thenucleation film is not necessarily required. Instead of forming thenucleation film, a SiH₄ gas may be supplied into the processingcontainer 1 for a predetermined time to treat the surface of the waferW. The predetermined time is preferably, for example, about 300 secondsor more.

Further, in the present embodiment, there has been described the casewhere the AlN film and the tungsten film are formed by separate filmforming apparatuses. However, the present disclosure is not limitedthereto. For example, the AlN film and the tungsten film may be formedby a single film forming apparatus having a gas supply mechanism forforming an AlN film and a gas supply mechanism for forming a tungstenfilm. Further, the wafer W may be transferred through the respectivefilm forming apparatuses under the atmospheric pressure.

As described above, in the tungsten film forming method according to thepresent embodiment, a first film of an aluminum-containing material isformed on the surface of the wafer W disposed in the processingcontainer 1 and having the TiN film formed on the surface thereof, whileheating the wafer W in a reduced pressure atmosphere. Then, in thetungsten film forming method according to the present embodiment, atungsten film is formed on the first film. This makes it possible toreduce the resistance of the tungsten film even when the film thicknessis made small.

In addition, in the tungsten film forming method according to thepresent embodiment, at least one of an AlCl₃ gas and a TMA gas, and areducing gas are supplied into the processing container 1 to form an AlNfilm as a first film. As a result, the orientation of the TiN film iscanceled by the AlN film, and the grains of deposited tungsten can becaused to grow large. This makes it possible to reduce the resistance ofthe tungsten film.

Further, in the tungsten film forming method according to the presentembodiment, after the formation of the first film and before the step offorming the tungsten film, a WF₆ gas and a SiH₄ gas are supplied intothe processing container 1 to form an initial tungsten film for formingtungsten nuclei on the surface of the wafer W, or a SiH₄ gas is suppliedinto the processing container 1 to treat the surface of the wafer W.Thus, it is possible to enhance the adhesion of tungsten to bedeposited. In addition, it is possible to enhance the uniformity oftungsten to be deposited.

Although the embodiment has been described above, various modificationsmay be made without being limited to the above-described embodiment. Forexample, although a semiconductor water has been described as an exampleof a substrate, the semiconductor wafer may be silicon, or a compoundsemiconductor such as GaAs, SiC, GaN or the like. Furthermore, thesubstrate is not limited to the semiconductor wafer. The presentdisclosure may also be applied to a glass substrate used for an FPD(flat panel display) such as a liquid crystal display device or thelike, a ceramic substrate, and the like.

According to one aspect of the tungsten film forming method disclosedherein, it is possible to reduce the resistance of a tungsten film evenwhen the tungsten film is made thin.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the disclosures. Indeed, the embodiments described herein maybe embodied in a variety of other forms. Furthermore, various omissions,substitutions and changes in the form of the embodiments describedherein may be made without departing from the spirit of the disclosures.The accompanying claims and their equivalents are intended to cover suchforms or modifications as would fall within the scope and spirit of thedisclosures.

What is claimed is:
 1. A tungsten film forming method using a filmforming apparatus, wherein the film forming apparatus apparatus includesa processing container, an exhaust part, a heating mechanism, a gassupply mechanism including an aluminum-containing gas supply source, anda tungsten-containing gas supply source, the method comprising: forminga first film of an aluminum-containing material on a surface of asubstrate having a TiN film, the TiN film being formed on the substratein the processing container while heating the substrate in a reducedpressure atmosphere; and forming a tungsten film on the first film inthe processing container while heating the substrate having the firstfilm formed thereon in a reduced pressure atmosphere.
 2. The method ofclaim 1, wherein in the act of forming the first film, a reducing gasand at least one of an AlCl₃ gas and a TMA (trimethylaluminum) gas aresupplied into the processing container to form an AlN film as the firstfilm.
 3. The method of claim 1, wherein in the act of forming the firstfilm, a reducing gas and at least one of an AlCl₃ gas and a TMA(trimethylaluminum) gas are alternately supplied into the processingcontainer with supply of a purge gas interposed therebetween form an AlNfilm as the first film.
 4. The method of claim 1, wherein in the act offorming the first film, a pressure inside the processing container is0.1 to 10 Torr.
 5. The method of claim 1, wherein the first film has athickness of 1 to 2 nm.
 6. The method of claim 1, further comprising:after forming the first film and before forming the tungsten film,supplying a WF₆ gas and a SiH₄ gas into the processing container to forman initial tungsten film for generating tungsten nuclei on the surfaceof the substrate.
 7. The method of claim 1, further comprising: afterforming the first film and before forming the tungsten film, supplying aSiH₄ gas into the processing container to treat the surface of thesubstrate.
 8. The method of claim 1, wherein the act of forming thefirst film and the act of forming the tungsten film are performedwithout breaking vacuum.
 9. The method of claim 2, wherein the reducinggas is an NH₃ gas.
 10. The method of claim 3, wherein the reducing gasis an NH₃ gas.
 11. The method of claim 6, wherein in the act of formingthe initial tungsten film, the WF₆ gas and the SiH₄ gas are alternatelysupplied into the processing container with supply of a purge gasinterposed therebetween.
 12. The method of claim 6, wherein in the actof forming the initial tungsten film a pressure inside the processingcontainer is 1 to 100 Torr.
 13. The method of claim 6, wherein theinitial tungsten film has a thickness of 0.5 to 5 nm.
 14. A film formingsystem, comprising: a first film forming apparatus including a firstprocessing container, a first exhaust part, a first heating mechanismand a first gas supply mechanism including an aluminum-containing gassupply source; a second film forming apparatus including a secondprocessing container, a second exhaust part, a second heating mechanismand a second gas supply mechanism including a tungsten gas supplysource; and a control part, wherein the control part is configured tocontrol the first exhaust part, the first heating mechanism, the firstgas supply mechanism, the second exhaust part, the second heatingmechanism and the second gas supply mechanism so as to perform: forminga first film of an aluminum-containing material on a surface of asubstrate having a TiN film formed thereon in the first processingcontainer while heating the substrate in a reduced pressure atmosphere;and forming a tungsten film on the first film in the second processingcontainer while heating the substrate having the first film formedthereon in a reduced pressure atmosphere.
 15. The system of claim 14,wherein the first gas supply mechanism further includes analuminum-containing gas supply source configured to supply at least oneof an AlCl₃ gas and a TMA (trimethylaluminum) gas into the firstprocessing container and a reducing gas supply source configured tosupply a reducing gas into the first processing container, and thecontrol part controls the first gas supply mechanism so as to supply atleast one of the AlCl₃ gas and the TMA gas and the reducing gas into thefirst processing container to form an AlN film as the first film. 16.The system of claim 14, wherein the first gas supply mechanism furtherincludes an aluminum-containing gas supply source configured to supplyat least one of an AlCl₃ gas and a TMA (trimethylaluminum) gas into thefirst processing container, a reducing gas supply source configured tosupply a reducing gas into the first processing container and a purgegas supply source configured to supply a purge gas into the firstprocessing container, and the control part controls the first gas supplymedia so as to alternately supply at least one of the AlCl₃ gas and theTMA gas and the reducing gas into the first processing container withthe supply of the purge gas interposed therebetween to form an AlN filmas the first film.
 17. The system of claim 14, wherein the control partcontrols the first exhaust part so that a pressure inside the firstprocessing container becomes 0.1 to 10 Torr in the act of forming thefirst film.
 18. The system of claim 14, wherein the control partcontrols the first exhaust part, the first heating mechanism and thefirst gas supply mechanism so that the first film has a film thicknessof 1 to 2 nm.
 19. The system of claim 14, wherein the second gas supplymechanism further includes a WF₆ gas supply source configured to supplya WF₆ gas into the second processing container and a SiH₄ gas supplysource configured to supply a SiH₄ gas into the second processingcontainer, and the control part controls the second gas supply mechanismso as to, before the act of forming the tungsten film, supply the WF₆gas and the SiH₄ gas into the second processing container to form aninitial tungsten film for generating tungsten nuclei on the surface ofthe substrate.
 20. The system of claim 14, wherein the second gas supplymechanism includes a gas supply source configured to supply a SiH₄ gasinto the second processing container, and the control part controls thesecond gas supply mechanism so as to, before the act of forming thetungsten film, supply the SiH₄ gas into the second processing containerto treat the surface of the substrate.
 21. The system of claim 14,further comprising: a vacuum transfer chamber to which the first filmforming apparatus and the second film forming apparatus are connected,and a transfer mechanism configured to transfer the substrate betweenthe first film forming apparatus, the second film forming apparatus andthe vacuum transfer chamber, wherein the control part controls thetransfer mechanism, the first exhaust part and the second exhaust partso that the act of forming the first film and the act of forming thetungsten film are performed without breaking vacuum.
 22. The system ofclaim 15, wherein the reducing gas is an NH₃ gas.
 23. The system ofclaim 16, wherein the reducing gas is an NH₃ gas.
 24. The system ofclaim 19, wherein the second gas supply mechanism further includes apurge gas supply source configured to supply a purge gas into the secondprocessing container, and the control part controls the second gassupply mechanism so as to, in the act of forming the initial tungstenfilm, alternately supply the WF₆ gas and the SiH₄ gas into the secondprocessing container with the supply of the purge gas interposedtherebetween.
 25. The system of claim 19, wherein the control partcontrols the second exhaust part so that a pressure inside the secondprocessing container becomes 1 to 100 Torr in the act of forming theinitial tungsten film.
 26. The system of claim 19, wherein the controlpart controls the second exhaust part, the second heating mechanism andthe second gas supply mechanism so that the initial tungsten film has afilm thickness of 0.5 to 5 nm.
 27. A film forming apparatus, comprising:a processing container; an exhaust part; a heating mechanism; a gassupply mechanism including an aluminum-containing gas supply source anda tungsten-containing gas supply source; and a control part, wherein thecontrol part is configured to control the exhaust part, the heatingmechanism and the gas supply mechanism so as to perform: forming a firstfilm of an aluminum-containing material on a surface of a substratehaving a TiN film formed thereon in the processing container whileheating the substrate in a reduced pressure atmosphere; and forming atungsten film on the first film in the processing container whileheating the substrate having the first film formed thereon in a reducedpressure atmosphere.
 28. The apparatus of claim 27, wherein the gassupply mechanism further includes an aluminum-containing gas supplysource configured to supply at least one of an AlCl₃ gas and a TMA(trimethylaluminum) gas into the processing container and a reducing gassupply source configured to supply a reducing gas into the processingcontainer, and the control part controls the gas supply mechanism so asto supply at least one of the AlCl₃ gas and the TMA gas and the reducinggas into the processing container to form an AlN film as the first film.29. The apparatus of claim 27, wherein the gas supply mechanism furtherincludes an aluminum-containing gas supply source configured to supplyat least one of an AlCl₃ gas and a TMA (trimethylaluminum) gas into theprocessing container, a reducing gas supply source configured to supplya reducing gas into the processing container and a purge gas supplysource configured to supply a purge gas into the processing container,and the control part controls the gas supply mechanism so as toalternately supply at least one of the AlCl₃ gas and the TMA gas and thereducing gas into the processing container with the supply of the purgegas interposed therebetween to form an AlN film as the first film. 30.The apparatus of claim 27, wherein the control part controls the exhaustpart so that a pressure inside the processing container becomes 0.1 to10 Torr in the act of forming the first film.
 31. The apparatus of claim27, wherein the control part controls the exhaust part, the heatingmechanism and the gas supply mechanism so that the first film has a filmthickness of 1 to 2 nm.
 32. The apparatus of claim 27, wherein the gassupply mechanism further includes a WF₆, gas supply source configured tosupply a WF₆ gas into the processing container and a SiH₄ gas supplysource configured to supply a SiH₄ gas into the processing container,and the control part controls the gas supply mechanism so as to, afterthe act of forming the first film and before the act of forming thetungsten film, supply the WF₆ gas and the SiH₄ gas into the processingcontainer to form an initial tungsten film for generating tungstennuclei on the surface of the substrate.
 33. The apparatus of claim 27,wherein the gas supply mechanism further includes a SiH₄ gas supplysource configured to supply a SiH₄ gas into the processing container,and the control part controls the gas supply mechanism so as to, beforethe act of forming the tungsten film, supply the SiH₄ gas into theprocessing container treat the surface of the substrate.
 34. Theapparatus of claim 27, wherein the control part controls the exhaustpart so that the act of forming the first film and the act of formingthe tungsten film are performed without breaking vacuum.
 35. Theapparatus of claim 28, wherein the reducing gas is an NH₃ gas.
 36. Theapparatus of claim 29, wherein the reducing gas is an NH₃ gas.
 37. Theapparatus of claim 32, wherein the gas supply mechanism further includesa purge gas supply source configured to supply a purge gas into theprocessing container, and the control part controls the gas supplymechanism so as to, in the act of forming the initial tungsten film,alternately supply the WF₆ gas and the SiH₄ gas into the processingcontainer with the supply of the purge gas interposed therebetween. 38.The apparatus of claim 32, wherein the control part controls the exhaustpart so that a pressure inside the processing container becomes 1 to 100Torr in the act of forming the initial tungsten film.
 39. The apparatusof claim 32, wherein the control part controls the exhaust part, theheating mechanism and the gas supply mechanism so that the initialtungsten film has a film thickness of 0.5 to 5 nm.